Hollow chain links that are intertwined to form jewelry rope chains are usually formed by first extruding a flat sheet of material between an outer die and a metal former to create an elongated wire. The resultant wire is formed with an opening or a seam that will eventually allow for the passage of the metal former when exposed to an acid, as is known in the art. Such wire is then usually formed into a coil on a mandril and then cut into individual links. Because of the spiral configuration, one end of each link will be slightly offset from the other end of such link. Prior to use, such links are made planar. In doing so, however, the wire itself is also slightly squashed. However, the cross-section of such links are still generally of an annular, toroidal configuration and are generally referred to as annular.
Thus, such links are generally annular in profile and annular in cross-section. The cross-sectional surface area of a seamed link having an annular cross section will generally be defined as .pi.(r.sub.2.sup.2 -r.sub.1.sup.2) minus the seam, where r.sub.2 -r.sub.1 designates the thickness of the sheet of material used to form the wire and the link. When the seam is rather minimal, as is the case with most prior art chain links, the cross-sectional surface area will approach that of a seamless, annular cross-section hollow link, or .pi.(r.sub.2.sup.2 -r.sub.1.sup.2). Seamless hollow links are, however, not favored in the art, as discussed in U.S. Pat. No. 4,651,517 to Benhamou et al. and U.S. Pat. No. 5,129,220 to Strobel, because a seam accelerates the dissolving of the metal former used to create the wire.
Significant advances in the jewelry rope chain art are defined by the look of the resultant product and the method of making the same. Hollow-link rope chains advanced the art over solid-link rope chains by producing a chain with a similar appearance at a fraction of the cost. A chain worn around a person's neck will usually be admired more for its appearance than its weight, and a lighter chain provided at a reduced price, having the appearance of a heavier chain provided at a much higher price, will always benefit the consumer. Consequently, great attention has been paid to the method of manufacturing and forming the links that are intertwined into rope chains, with improvements or enhancements in each link resulting in a rope chain that is, on the whole, improved or enhanced over the prior art.
In an effort to produce a rope chain that is an improvement over the prior art, the present inventor has devised a way to produce a full-bodied rope chain with a reduction in the amount of material used to form the links. The present inventor accomplishes such task by forming intertwinable links from a wire with a non-annular, U-shaped cross section having an interconnecting portion, a pair of substantially straight leg portions, and an enlarged seam portion, not known before in the art. The enlarged seam portion allows for even quicker dissolving of the metal former, and the U-shaped cross section, as compared with an annular cross section, provides a much snugger, more abutting fit between intertwinable links assembled into a rope chain. Also, as will be described in more detail below, the U-shaped cross section provides a reduction in the amount of precious metal used, providing a surface area that is below the .pi.(r.sub.2.sup.2 -r.sub.1.sup.2) approached by an annular link with a minimal seam.
As noted above, link segments are, in general, squashed slightly after separation from an initial, unitary coil configuration to make them planar. Thus, while the initial formation of the wire cross-sectional configuration of one embodiment of the present invention has a semi-spherical interconnecting bight portion, the slight squashing will make the bight portion slightly into an oval shape, and will actually elongate the legs, so that the legs wind up even slightly longer than when initially formed. Thus, the U-shaped cross-sectional configuration will result in links that are squashed in cross-section. The elongated legs result in a rope chain having a full-body appearance, and also allow for a snugger fit between intertwined chain links assembled in a rope chain. The snugger fit realized by the U-shaped cross sectional wire will be recognized in the manner in which a straight side lies best again another straight surface side, which is absent from a rope chain formed from chain links having an annular, toroidal configuration, where only point contact is made between abutting annular, toroidal links. As the significant advance of the present invention is in the use of the straight legs, the interconnecting portion need not be arcuate, but could also be of other shapes including oval or the like.
In the case of annular, toroidal cross-sectional configured links, it is often desired to simulate the facets found on the outside of a solid rope chain. In solid rope chains, the facets are formed by actually cutting off a portion of the exterior surface of selected links. With hollow rope chain, such cutting would perforate the wall of the link.
Various methods have been suggested to simulate such facets on hollow rope chain. One method is suggested in U.S. Pat. No. 5,125,225, U.S. Pat. No. 5,129,220 and U.S. Pat. No. 5,353,584, all to Strobel. In those patents, it is suggested to flatten the links by incrementally pounding on the surface. Other methods have also been suggested.
In classical rope chain, both hollow and solid, these facets or simulated facets occur in the outer portion of the links which form the exterior surface of the rope chain when assembled. In the present invention, there also exists the interconnecting portion as the exterior of the rope chain when assembled. Simulated facets can then also be made on such interconnecting portions, just as in classical rope chain.
Thus, through the use of the U-shaped cross-section for the links forming a rope chain, the present inventor still gets the interconnecting portion forming the exterior as in classical rope chain, but also gets a snugger fitting construction because of the elongated straight legs, and less precious metal because of the reduced cross-sectional area.